Does Oil Brand Matter?

Does motor oil brand really matter?As far as comparing conventional oils.Not conventional vs. synthetic and using the major brands Castrol, Mobil, Havaline,Valvaline,etc. Highest API ratied stuff. Not the no name SF rated convience store stuff. I've always been a diehard Castrol GTX user but with prices going up some others are cheaper. Mobil Clean 5000 is 46 cents cheaper. I've always heard don't switch brands but does it matter? Can a person run whatever is cheapest at each oil change with no ill effects? Your thoughts? Thanks.

honestly? its all just about the exact same at this point. but i will never stop using castrol GTX in rotaries.

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2006-2010 UofA FSAE
Powertrain Director
"just to let you know, if you just drove away in your car, a few car alarms and some angry people went off"
Jesus christ they for some reason made me an engineer...

Besides the SAE and API ratings, there are many other factors like detergents, purity, film strength, stability, volatility, etc. You can research many of these factors on the internet by surfing various oil vendor websites (especially synthetic oil vendors), although any information will obviously be slanted toward their product. Most RX-7 owners like Castrol GTX because it holds up very well to the rotary engine's shearing tendencies, and it is pretty good on sludge control. I am not aware of any leading brands of conventional oil that would hurt your engine.

when the mop is gone and you are premixing is it better to use synthetic oils? I know this is a newb question but I've often wondered this. Since those that premix don't have to worry about if the oil is good or bad at burning then we are free to use whatever oil best suits the internals of the engine. So this being said is synthetic better on bearings, rotors, turbos etc... I seem to remember hearing something about synthetic is very bad for the carbon seal inside of turbos, is this correct?

you really want something that burns and burns clean if you are using the stock metering oil pump. If you don't premix then really some of the best oil to use is castrol gtx. Most of the synthetic oils out there are made not to burn witch is not good for the rotary unless you are premixing.